WO 2009/075999 discloses a high-pressure discharge lamp in which a metal halide fill is used. In order to assist the cycle process, the high-pressure discharge lamp contains WO3 or WO2X2 with X selected from Cl, Br, I. The discharge vessel is ceramic, and rare earth metals must be avoided. Similar content is found in U.S. Pat. No. 6,362,571 and U.S. Pat. No. 6,356,016.
U.S. Pat. No. 7,057,350 discloses a high-pressure discharge lamp in which a metal halide fill is used. The discharge vessel is ceramic, and rare earth metals may be used owing to the high wall loading, which releases oxides from the ceramic that can assist a cycle process.
JP 57-128 446 discloses a metal halide lamp which, in the case of a quartz glass discharge vessel, uses WO2I2 in order to assist the cycle process.